1. Technical Field
The present invention is related to a method for mixing of two fluids and an apparatus for performing such a method.
The invention is especially related to mixing of water (salt water and/or fresh water) with a gas such as oxygen or carbon dioxide. The use of the invention can be related to water treatment such as treatment of drinking water, wastewater, process water or treatment of water to be used in connection with farming/treatment of aquatic animals. The invention can be used also for process water containing particles or fibers.
2. Description of the Related Art
U.S. Pat. No. 4,210,534 concerns an oxygenation system for supply of oxygen to wastewater. Water and air are supplied to a horizontal mixing chamber respectively by help of a central nozzle and an annular chamber coaxially arranged. The mixing chamber is shaped with tapered converging walls in two stages with a cylindrical shape downstream of this. The mixing chamber has in addition equipment such as a submerged pump, a source of pressurised air, and is collected by a floating construction. The described mixing chamber has a relatively complex geometry, and relatively high production costs must be expected as this structure is either produced by casting or machining. Further, the shape of the mixing chamber with graduate cross sectional area will result in an energy demanding pressure loss.
U.S. Pat. No. 4,735,750 discloses a process and device for the dissolution of gas in liquid. The liquid is introduced under pressure through a nozzle plate into a reaction space, where a mixture of gas and solution flow out through outlets laterally at the bottom into a solution tank and the gas recirculates through inlets at the top near the nozzle plate. The solution tank has a gas cushion and is filled to a level between inlet and outlet at a medium pressure. The dissolved body of gas is delivered subsequently via a gas flow regulator and the solution is drawn off from the solution tank at a low pressure level via a control valve as a supersaturated solution. The device has a complex reactor chamber design and where also level control is necessary. The device is not suitable for aeration of salt water or for fluids containing fibers, as the holes are easily clogged.
Swedish published patent application No. 375 704 describes a vertically arranged device for aeration of water. A nozzle for supply of finely distributed water droplets is arranged in the upper part of the device. The device is filled with water up to a gas cushion below the nozzle. When the droplets hit the surface of the fluid, gas is sucked into the water. The lower part of the device is either submerged in the water to be aerated or the fluid with gas bubbles is led to the water via a pipe. This device is an aerator with low dissolution capacity. It is operated at low pressure. The gas is not dissolved into the fluid, but is maintained as bubbles.